1. Field of the Invention
This invention relates to a cylinder lock having two sets of tumblers. More specifically, the invention relates to a lock having the conventional pin tumblers which work on the profile of the upper edge of the key and additional security or disc tumblers which work on a security contour cut on a lateral surface of the key. The invention also relates to a key for such a lock.
2. Description of the Prior Art
The prior art presents a number of cylinder locks having two sets of tumblers. An example is the recent U.S. Pat. No. 4,434,636 which issued Mar. 6, 1984 to Kurt Prunbauer. This patent discloses a cylinder having the conventional set of pin tumblers working along the profile of the edge of the key and a second set of angled pin tumblers located entirely within the cylinder and aimed down at an enlarged rib along the bottom opposite edge of the key, the rib being countoured and the pins designed with recesses adapted to receive a side bar with the result that when the recesses of the auxiliary pin tumblers are aligned, the side bars are permitted to yield inwardly to allow the key to rotate the cylinder core.
The Danish Pat. No. 73,832 which issued in Feb. 15, 1952 discloses a cylinder having a core with a special pin which laterally engages an indentation in the center of the key to manipulate a special auxiliary pin tumblers in addition to the conventional pin tumblers working against the top of the key.